MD Settings: polish up some top-level buttons

chrome/browser/resources/settings/privacy_page/privacy_page.html

 <link rel="import" href="chrome://resources/polymer/v1_0/polymer/polymer.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/iron-flex-layout/classes/iron-flex-layout.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/neon-animation/neon-animatable.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-button/paper-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-icon-button/paper-icon-button.html">
 <link rel="import" href="chrome://resources/polymer/v1_0/paper-item/paper-item-body.html">
 <link rel="import" href="chrome://md-settings/certificate_manager_page/certificate_manager_page.html">
 <link rel="import" href="chrome://md-settings/clear_browsing_data_page/clear_browsing_data_page.html">
 <link rel="import" href="chrome://md-settings/controls/settings_checkbox.html">
 <link rel="import" href="chrome://md-settings/settings_page/settings_animated_pages.html">
@@ skipping 72 matching lines @@
         <div class="settings-box two-line" on-tap="onSiteSettingsTap_">
           <div class="start">
             <div i18n-content="siteSettings"></div>
             <div class="secondary">
               <!-- TODO(dschuyler) replace this placeholder text -->
               Contrary to popular belief, Lorem Ipsum is not simply random text.
             </div>
           </div>
         </div>
         <div class="settings-box">
-          <paper-button on-tap="onClearBrowsingDataTap_"
+          <paper-button on-tap="onClearBrowsingDataTap_" class="primary-button"
               i18n-content="clearBrowsingData">
           </paper-button>
         </div>
       </neon-animatable>
       <neon-animatable id="manage-certificates">
         <settings-subheader i18n-values="page-title:manageCertificates">
         </settings-subheader>
         <settings-certificate-manager-page>
         </settings-certificate-manager-page>
       </neon-animatable>
@@ skipping 112 matching lines @@
       <neon-animatable id="clear-browsing-data">
         <settings-subheader i18n-values="page-title:clearBrowsingData">
         </settings-subheader>
         <settings-clear-browsing-data-page prefs="{{prefs}}">
         </settings-clear-browsing-data-page>
       </neon-animatable>
     </settings-animated-pages>
   </template>
   <script src="privacy_page.js"></script>
 </dom-module>